Air treatment devices with use-up indicators

摘要

An air treatment chemical dispensing device (10) comprises a substrate (22) bearing a volatile air treatment chemical capable of being dispensed from the substrate (22) when the substrate is heated and a housing (12) preferably enclosing a heater (56) positioned proximate to the substrate (22), to heat the substrate (22), the housing (12) having a series of vents (30) allowing in air from the environment and permitting the air to pass through along with the air treatment chemical dispensed from the substrate (22). The substrate (22) is shaped to have a forward frustum shaped section (23) and a rearward projecting nose (25) positioned closely adjacent the heater (56) with room around the nose (25) for air to pass around its periphery.